Selector valve with snubbing action



J n- 13, 19 P. B. SHUTT 2,868,174

SELECTOR VALVE WITH SNUBBING ACTION Filed June 25, 1957 INVENTOR.

P40; 5. 27/077 BY ATTOPA/f) approaches its valve seat.

United StatesPatent 2,868,174 Patented Jan. 13, 1 959 fi ice Paul B.Shutt, St. Joseph, Mich., assignor to Bendix Aviation Corporation, SouthBend, Ind., a corporation of Delaware Application June 25, 1957, SerialNo. 667,923 6 Claims. (Cl. 121-40) The present invention relates tovalves having so-called lock out means therein for preventing returnflow through the valve; and more particularly to valves of the abovetype having means which will prevent the lock out valve from slammingshut against its seat during stoppage of the reverse flow through thevalve.

When valves of the above described type are used for controlling flow toand from fluid pressure motors which actuate large masses in whichconsiderable momentum can be developed, and more especially with liftcylinders used to raise heavy loads in farm machinery and the like,extremely high pressures can be developed should the control valvesuddenly be slammed shut when the load is being lowered and return flowfrom the lift cylinder is being experienced through the valve. In mostcontrol valves of this type there is provided a so-called lock out valveusually of a poppet type construction which acts very much like a checkvalve to prevent leakage or return flow from the lift cylinder when thecontrol valve is in its normal or non-actuating condition. The so-calledlock out valves are usually necessary to hold the load in any givenposition, inasmuch as the control valve usually used in such systemscannot be made leakage tight. One of the difficulties with the prior artstructures with which I am familiar, develops when the control valvebegins to throttle off the return flow from the lift cylinder, at whichtime the so-called ,lock out valve slams shut to abruptly stop thereturn flow of fluid from the lift cylinder, thereby causing the load tobe abruptly stopped and thereby subjecting portions of the system toextremely high pressures.

A principal object of the present invention is the provision of a newand improved control valve having lock out means which will not slamshut when the control valve is moved to its neutral or non-actuatingcondition of the control fluid pressure motor.

Another object of the present invention is the provision of anew andimproved control valve of the above described type having a movable wallor piston in a flow chamber which will be biased up against and hold thelock out valve off its seat when the control valve is in a positionadapted to permit lowering of the load; and which control valve whenmoved into its normal or nonactuating position establishes a restrictedflow path for the return fluid, while at the same time trapping fluid onthe opposite side of said movable wall from said lock out valve in amanner causing the trapped fluid t-o flow through a restriction tothereby prevent the lock out valve from slamming shutthe movable wallpreferably having a projection which may be moved through a valve portto lift the lock out valve from its seat and which movable member formsa flow restriction with respect to the valve port when the movable wallbegins to withdraw from the port to restrict return flow when the lockout valve Another object of the present invention is the provi type inwhich the movable wall projects through a valve port to lift the lockout valve from its valve seat, and in which the control valve does notcompletely shut off the return flow of fluid through the lock out valvewhen moved to its neutral or non-actuating position; the improved valvefurther causing fluid to be trapped behind the opposite side of themovable wall when the control valve is moved to its neutral position andto force the trapped fluid through a flow restriction in a mannerproducing a force tending to oppose the closing of the lock out valveand thereby slowly permit the lock out valve to abut its valve seat.

The invention resides in certain constructions and combinations andarrangements of parts, and further objects and advantages of the presentinvention will become apparent to those skilled in the art to which theinvention relates from the following description of the preferredembodiment described with reference to the accompanying drawing fiorminga part of this specification.

The improved valve structure shown in the drawing generally comprises acontrol valve A which in one position will conduct flow from a pump 16to a single acting lift cylinder 12 such as is used for the raising andsupporting of loaders on farm tractors, and the like. The control valveA has a second position for permitting the lowering of the load, inwhich position return flow from the lift cylinder 12 is conductedthrough the control valve A to the reservoir 14 which supplies hydraulicfluid for the pump 10. Operatively positioned between the control valveA and the lift cylinder 12 is a lock out valve B which, when in itsclosed position, prevents leakage of return fluid from the lift cylinder12 to the control valve A such that its load can be held in anyposition. When the control valve A is moved into a third position, flowto the lift cylinder is prevented, and the lock out valve is permittedto close, thereby preventing return flow from the lift cylinder 12.

While the control valve A and the lock out valve B may be made asseparate units connected by suitable conduit means, the preferredembodiment shown in the drawing combines the two within a single bodymember 16. The portion of the body member 16 forming the lock out valveB is formed by a longitudinal stepped bore or flow chamber 18, and anannular member 2% having a centrally located valve port 22 therein ispositioned against the shoulder 24 provided by the stepped portion ofthe bore 1%. A movable wall or piston 26 is positioned in the bottom orsmall diameter section 23 of the stepped bore 18, and is provided with acentrally located boss or projection 36 which is capable-of being movedthrough the valve port 22. The side of the annular member 20 which isopposite the piston 26 is bevelled at approximately a 45 angle in theregion surrounding the valve port 22 to provide a valve seat 32 againstwhich a ball valve 34 is biased by coil spring 36. The outer end of theenlarged diameter section 38 of the stepped bore 18 is closed off bymeans of a cup shaped closure member 40 which is held in place by a snapring 42, and which supports the coil spring 36 for abutment with theball valve 34. Unrestricted flow communication is provided between theportion of the flow chamber provided by its large diameter section 38(the portion above the ball valve 34 as seen in the drawing) and thelift cylinder 12 by means of a connection 44- in the body member 16, andsuitable porting 46 in the side Walls of the cup shaped closure member4i An O-ring seal 48 is provided the annular sion of a new and improvedvalve of the above described member 29, to prevent leakage around theside edges of the member 20 in which the valve seat 22 isformed.

The control valve A shown in the drawing is a slide valveformed by meansof a cylindrically shaped slide 50 positioned in a longitudinal bore 52extending generally parallel with respect to the stepped bore 18. Theside walls 54 of the longitudinal bore 52 are provided with a pluralityof annular recesses forming a return port 56, a first motor port 53, apressure port 60, a port 62 for the piston 26, and aireturn port 64arranged in that order proceeding in the axial direction of the steppedbore 18. The return port 56 is of course adapted to return fluid to thereservoir 14; the first motor port 58 is connected with the smalldiameter section 28 of the flow chamber 18 immediately beneath the valveport 22; the pressure port 6.6 is adapted to be connected with the pumpthe port 62 is connected with the bottom end of the stepped bore 18 bymeans of a suitable passageway 68; and the return port 64. iscommunicated with a return connection 76 by a passageway 72.

The lower end of the slide 56 is provided with a reduced diametersection 74- for the accommodation of a centering spring 76 adapted tohold the slide 56 in its previously referred to neutral or non-actuatingcondition. The lower end of the longitudinal bore 52 is provided with adouble stepped counterbore, the smaller diameter section 86 of which ismade coextensive with the reduecd diameter section 74 of the slide 56.An annular washer 82 is positioned in the annular space provided by thereduced diameter section it and the smaller diameter section 86 of thedouble stepped counterbore, and is biased into engagement with theshoulders so provided in the slide and body member by the coil spring'76. The lower end of the coil spring 76 is abutted by a similar annularwasher 86 which in turn is supported by an annular sealing member 88adjacent the lower end of the smaller diameter section 86 of the doublestepped bore 78. The annular sealing member 68 is in turn held in placeby a cup-shaped closure member 96 positioned in the lower or largerdiameter section 92 of the double stepped bore 78. The cup-shapedclosure member 96 is held in place by a snap ring 94, and the upper endof the closure member 26 abuts both the shoulder as provided by thedouble stepped bore and the annular sealing member 88 to retainthesealing member 86 in position and limit its movement in a downwarddirection. The lower end of the slide 56 is in turn provided with a snapring 96 which may abut the radially inner edges of the sealing member 88to oppose upward movement of the slide 50. Movement of the slide 56 inan upward direction causes the sealing member 86 to compress the coilspring 76, inasmuch as the upper end of the coil spring 76 will beconfined by the upper shoulder of the double stepped bore 78. Downwardmovement of the slide causes the shoulder on the slide to move the upperend of the spring 76 downwardly, while the annular sealing member 88 isheld stationary by the cupshaped closure member 90. It will therefore beseen that the spring 76 will move the slide 56 into its neutral ornon-actuating condition when no external actuating forces are applied tothe slide.

The slide valve structure is completed by a plurality of cooperatingrecesses in the slide 56 comprising a return groove 98, apressure groove100, and a return groove 102 positioned in the same order as indicatedfor the recesses in the side walls of the valve bore. In the neutralposition of the slide 50, the upper return groove and recesses 98 and 56of the slide and bore, respectively, will be generally opposite eachother; the pressure groove 160 and recess 66 will be opposite eachother; the lower return groove 102 and recess 64 will be opposite eachother; and the first motor port 53 and piston port 62 will be valved offby means of suitable land portions on the slide 50.

When the slide 50 is moved into its upper position: the return groove102 will communicate the return port 64 with the piston ports 62; thepressure groove 160 will communicate the pressure port 60 with the firstmotor port 58; and the motor port 58 will be isolated from the .Wlll bedelivered to the upper portion of the piston 26 while the lower portionof the piston will be communicated with the system reservoir 14. Thepiston 26 will therefore be held into its lower position; and the pumppressure in the upper end of the small diameter section 28 of the flowchamber will force the ball valve 34 off its seat 32 to permit full flowof pump pressure to the single acting lift cylinder 12.

When the slide 50 is moved into its downward position: the return groove98 will communicate the first motor port 58 with the return port 56; thepressure groove 100 will communicate the piston port 62 with thepressure port 60; and the return groove 102 communicates only with thereturn port 64. In the downward position, therefore, the slide 56 causespressure to be delivered to the lower end of the piston 26 forcing itupwardly to unseat the ball valve 34 from its valve seat 32. Return fiowfrom the lift cylinder 12 may therefore be established through the valveport 22 past the projection 36 of the piston 26, through the passageway66 and groove 98, to the return port 56 leading to the reservoir 14. Theload upon the power lift cylinder will cause flow through this path toproceed fairly rapidly whereby considerable downward momentum will bedeveloped in the load supported by the power lift cylinder.

When downward actuating force on the slide 56 is released, the slide 50will be immediately shifted by the coil spring '76 to its neutral onnon-actuating condition previously referred to. In this condition, thepiston port 62 is closed off with the piston 26 in its extended positionbiasing the ball valve 34 out of engagement with the seat 26. The fluidbeneath the piston 26 will therefore be trapped in place were it not forthe provisionof a flow restricting passageway 1M communicating the lowerend of the piston 26 with the pasageway 66. The flow restrictingpassageway 104 is formed by a longitudinal drilling in the lower end ofthe piston 26, and a small diameter transverse drilling 166 which willrestrict flow from the bottom end of the piston 26 into the passageway66 sufliciently to develop enough pressure differential across thepiston 26 to oppose and slow down movement of the ball 34 towards itsseat 32. To further facilitate the slowing down of the piston and thepower lift cylinder 12, an additional flow restricting passageway 168 ispositioned in the slide Stir-which passageway communicates its landportion which closes off the first motor port 58' in its neutralposition with the slide return groove 98.

It will be seen that there are in effect two flow restrictions to thereturn flow from the single lift cylinder 12 when the ball valve 34 isbiased of"? of its seat by means of the piston 26, and the slide 56 isfirst moved to its eutral or non-actuating position. The first of theserestrictions is provided by means of an annular space between theprojection 36 of the piston 26, and the side walls of the valve port 22;and the second of which is provided by the flow restricting passageway168 in the slide valve 56. The combined resistance of these two flowrestriction will be designedto provide a terminal downward velocity ofthe lift cylinder 12 which. will be acceptable in the particular systemin which the valve is to be installed. In the embodiment shown in thedrawing, the major amount of restriction to the return flow from thepower .lift cylinder 12 is provided by means of the passageway 108 andonly a minor amount of the flow restriction is provided by means of theclearance between the port 22 and projection 30 of the piston 26. Thiswas done because of the stack-up of tolerances Which may be experiencedin the manufacturing N t ces of the valve. It has been established thatthe quantity of fluid passing through the valve port 22, when theprojection 30 is positioned to one side of the opening, may beapproximately 2.5 times that experienced when the projection 30 iscentrally located with respect to the valve port 22. Inasmuch as thelocation of the projection 30 with respect to the valve port 22 isdetermined by a stack-up of manufacturing tolerances, the flowrestriction so provided by the projection 30 and valve port 22 will notpreferably be relied upon to produce a major portion of the totalresistance to return flow from the power lift cylinder 12.

By way of further refinement, the upper end of the projection 30 may beslightly enlarged with respect to the remainder of the projection 30such that its throttling action will be confined to the position of thepiston 26 wherein the ball piston 34 approaches its seat 32. When theball piston approaches its seat, a throttling of the reverse flow occursbetween the :ball and its seat which tends to slam the ball 34 intoengagement withits seat. Because these forces across the ball 34increase rapidly as the ball approaches its seat, only the tip portionof the projection 30 need be enlarged to provide the above referred torestriction; and of course when full flow is desired through the lockout valve B, the piston 26 will be forced upwardly sufficiently to movethe ball and tip portion of the projection 30 clear of the valve seat32. In this upper position, the reduced diameter center section of theprojection 30 will extend through the valve port 22 such thatsubstantially no flow restriction is experienced when the ball is heldin its upper fully released position.

It will be apparent that the flow restriction as provided by thepassageway 108 need not necessarily be confined to the slide portion 50of the valve structure, but may be positioned anywhere in a second flowpath which is communicated with the passageway 66 when the valve is inits neutral position. This restriction could occur any where in thissecond flow path which of course would include positions outside of thebody member 16.

While the invention has been described in considerable detail, I do notWish to be limited to the particular constructionsshown and described,and it is my intention to cover hereby all novel adaptations,modifications and arrangement thereof which come within the practice ofthose skilled in the art to which the invention relates.

I claim:

1. In a fluid pressure control system having a lift cylinder with amovable wall therein to form an expansible chamber in Which the movablewall is biased into a retracted position or the equivalent for providingreverse flow; a source of fluid pressure, a valve body member having aflow chamber therein, a second movable wall in said flow chamberdividing said flow chamber into first and second opposing chambers andbeing adapted for longitudinal movement in said flow chamber, a valveseat in said first opposing chamber facing away from said second movableWall, a valve closure member on the other side ,of said valve seat fromsaid second movable wall, said valve closure member being biased againstsaid valve seat, said second movable wall being constructed and arrangedto abut said valve closure member and force it from its seat, flowconducting means communicating the opposite side of said valve seat fromsaid second movable wall to said expansible chamber of said liftcylinder, a first port in said first opposing chamber positioned in suchmanner as to communicate with said valve seat during the time saidclosure member is biased olf of its valve seat by said second movablewall, a second port in said second opposing chamber, valve meansconstruted and arranged to conduct pressure from said pressure source tosaid second port While permitting return flow out of said first portwhen said valve means is in one position, and closing off said secondport while permitting flow out of said first port when in a secondposition, means providing a restriction to flow out of said secondopposing chamber with said valve means in its second position, and meansforming a restriction to return flow from said lift cylinder during thetime in which said second movable wall moves in a direction permittingsaid valve closure member to approach its valve seat, whereby acushioning efiect is provided for said lift cylinder before return flowis stopped by said valve closure member.

2. In a hydraulic control system having a lift cylinder with a movablewall therein to form an expansible chamber in which the movable wall isbiased into a retracted position, or the equivalent for providingreverse flow: a source of hydraulic fluid pressure, a valve body memberhaving a flow chamber therein, a second movable wall in said flowchamber dividing said flow chamber into first and second opposingchambers and being adapted for I011- gitudinal movement in said flowchamber, a valve seat in said first opposing chamber facing away fromsaid second movable wall, a valve closure member on the other side ofsaid valve seat from said second movable wall, said 1 valve closuremember being biased against said valve seat,

said second movable wall being constructed and arranged to abut saidvalve closure member andforce it from its seat, flow conducting meanscommunicating the opposite 7 side of said valve seat from said secondmovable wall to saidexpansible chamber of said lift cylinder, a firstport in said first opposing chamber positioned in such mannor as tocommunicate with said valve seat during the time said closure member isbiased off of its valve seat by said second movable wall, a second portin said sec ond opposing chamber, valve means constructed and ar rangedto conduct pressure from said pressure source to said second port whilepermitting return flow out of said first port through a first flow pathwhen said valve means is in one position, and closing off said secondport while establishing flow out of said first port through a secondflow path when in a second position, means providing a restriction toflow out of said second opposing chamber with said valve means in itssecond position, and means providing a flow restriction in said secondflow path causing the rate of How out of said first port when said valveis in its second position to be less than when in its first position,and whereby said valve closure member is made to slowly approach itsvalve seat when said valve means i is moved into its second position.

3. In a hydraulic control system having a lift cylinder with a movablewall therein to form an expansible chamber in which the movable wall isbiased into a retracted position, or the equivalent for providingreverse flow: a source of hydraulic fluid pressure, a valve body memberhaving a flow chamber therein, a second movable wall in said flowchamber dividing said flow chamber into first and second opposingchambers and being adapted for longitudinal movement in said flowchamber, a valve seat in said first opposing chamber facing away fromsaid second movable Wall, a valve closure member on the other side ofsaid valve seat from said second movable wall, said valve closure memberbeing biased against said valve seat, said second movable wall beingconstructed and arranged to abut said valve closure member and force itfrom its seat, flow conducting means communicating the opposite sideofsaid valve seat from said second movable wall to said expansiblechamber of said lift cylinder, a first port in said first opposingchamber positio-nediin such manner as to communicate with said valveseat during the time said closure member is biased off of its valve seatby said second movable wall, a second port in said second opposingchamber, slide valve means constructed and arranged to conduct pressurefrom said pressure source to said second port while permitting returnflow out of said first port through a first flow path when said valvemeans is in one position, and closing 01f said second port whileestablishing flow out of said first port through a second flow pathlocated in said slide when said slide is in a second position, saidsecond flow path causing the rate of flow out of said port when saidvalve is in its second posltion to be less than when in. its firstpositron, and means providing a restriction to flow out of said secondopposing chamber with said slide valve means in its second position,whereby said'valve closure memher i made to slowly approach its valveseat when said valve means is moved into its second position.

4. In a hydraulic control system having a lift cylinder witha movablewall therein to form an expansible chamber in which the movable wall isbiased into a retracted position, or the equivalent for providingreverse fiow: a source of hydraulic fiuid pressure, a valve body memberhaving a flow chamber therein, a second movable wall in said flowchamber dividing said fio-w chamber into first and second opposingchambers and being adapted for longitudinal movement in said flowchamber, a valve seat in said first opposing chamber facing away fromsaid second movable wall, a valve closure member on the other side ofsaid valve seat from said second movable wall, said valve closure memberbeing biased against said valve seat, said second movable wall beingconstructed and arranged to be moved into said valve seat for abutmentwith said valve closure member to force it from its seat, said secondmovable wall forming a ilow restriction between itself and said seatwhen said closure member is held adjacent its seat by said secondmovable wall, flow conducting means communicating the opposite side ofsaid valve seat from said second movable wall to said expansible chamberof said lift cylinder, a first port in said first opposing chamberpositioned in such manner as to communicate with said valve seat duringthe time said closure member is biased off of its valve seat by saidsecond movable wall, a second port in said second opposing chamber,valve means constructed and arranged when in one position to conductpressure from said pressure source to said second port to cause saidsecond movable wall to move said valve closure member from its seatwhile permitting return fiow out of said first port through a first flowpath, and when in a second position to close oil said second port Whilealso establishing flow out or said first port, and means providing arestriction to flow out of said second opposing chamber with said valvemeans in its second position, whereby said valve closure member is madeto slowly approach its valve seat when said valve means is moved intoits second position.

5. In a hydraulic control system having a lift cylinder with a movablewall therein to form an expansible chamber in which the movable wall isbiased into a retracted position, or the equivalent for providingreverse flow: a source of hydraulic fiuid pressure, a valve body memberhaving a flow chamber therein, a second movable wall in said flowchamber dividing said flow chamber into first and second opposingchambers and being adapted for longitudinal movement in said flowchamber, a valve seat in said first opposing chamber facing away fromsaid second movable wall, a valve closure member on the other side ofsaid valve seat from said second movable wall, said valve closure memberbeing biased against said valve seat, said second movable wall beingconstructed and arranged to be moved into said valve seat for abutmentwith said valve closure member to force it from it seat, said secondmovable wall forming a flow restriction between itself and said seatwhen said closure member is held adjacent said seat by said secondmovable wall, flow conducting means communicating the opposite side ofsaid valve seat from said second movable wall to said expansible chamberof said lift cylinder, a first port in said first opposing chamberpositioned in such manner as to communicate with said valve seat duringthe time said closure member is biased off of its valve seat by saidsecond movable wall, a second port in said second opposing chamber,valve means constructed and arranged when in one position to conductpressure from said pressure source to said second port to cause saidsecond movable wall to move said valve closure member from its seatwhile permitting return flow out of said first port through a first fiowpath, and when in a second position to close oil said second port whilealso establishing flow out of said first port through a restricted flowpath, and means providing a supplemental flow restriction in saidrestricted flow path in addition to that between said second movablewall and said valve seat causing the rate of fiow out of said first portwhen said valve is in its second position to be less than when in itsfirst position, and means providing arestriction to flow out of saidsecond opposing chamber with said valve means in its second po ition,whereby said valve closure member is made to slowly approach its valveseat when said valve means is moved into its second position.

6. In a hydraulic control system having a lift cylinder with a movablewall therein to form an expansible chamber in which the movable wall isbiased into a retracted position, or the equivalent for providingreverse flow: a source of hydraulic fluid pressure, a valve body memberhaving a flow chamber therein, a second movable wall in said fiowchamber dividing said fiow chamber into first and second opposingchambers and being adapted for longitudinal movement in said flowchamber, a valve seat in said first opposing chamber facing away fromsaid second movable wall, a ball valve on the other side of said valveseat from said second movable wall, said ball valve being biased againstsaid valve seat, said second movable wall being constructed and arrangedto be moved into said valve seat for abutment with said ball valve toforce it from its seat, flow conducting means communicating the oppositeside of said valve seat from said second movable wall' to saidexpansible chamber of said lift cylinder,

a first port in said first opposing chamber positioned insuch manner asto communicate with said valve seat during the time said closure memberis biased 0d of its valve seat by said second movable wall, a secondport in said second opposing chamber, valve means constructed andarranged to conduct pressure from said pressure source to said secondport to cause said second movable wall to move said ball valve from itsseat while permitting return fiow out of said first port through a firstflow path,

and when in a second position to close off said second port Whileestablishing fiow out of said first port through a second flow path insaid valve means when said valve means is in a second position, saidsecond flow path caus w ing the rate of flow out of said first port whensaid valve is in its second position to be less than when in its firstposition, and means providing a restriction to fiow out of said secondopposing chamber with said valve in its second position, whereby saidball valve is made to slowly approach its valve seat when said valvemeans is moved into its second position.

No references cited.

